#define _CRT_SECURE_NO_WARNINGS
#ifdef _DEBUG
#define FILE_IN "input.txt"
#define FILE_OUT "output.txt"
#endif
#include <iostream>
#include <cstdlib>
#include <climits>
#include <set>
#include <map>
#include <cstdio>
#include <string>
#include <cstring>
#include <cassert>
#include <vector>
#include <algorithm>
using namespace std;
typedef long long ll;
const ll mod = 1000000007;
void openFiles() {
#ifdef _DEBUG
assert(freopen(FILE_IN, "r", stdin));
assert(freopen(FILE_OUT, "w", stdout));
#endif
}
void IOoptimize() {
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
}
struct Action {
int id;
int time;
bool type;
Action(int id, int time, bool type) : id(id), time(time), type(type) {}
};
bool operator<(const Action& a1, const Action& a2) {
return a1.time < a2.time;
}
bool get_bit(int mask, int i) {
return mask & (1 << i);
}
vector<Action> actions;
bool ok(int mask) {
vector<int> a[2];
for (auto act : actions) {
if (act.type) {
a[(int)get_bit(mask, act.id)].push_back(act.id);
}
else {
if (a[(int)get_bit(mask, act.id)].back() != act.id)
return false;
a[(int)get_bit(mask, act.id)].pop_back();
}
}
return true;
}
int main() {
openFiles();
IOoptimize();
int n;
cin >> n;
for (int i = 0; i < n; i++) {
int time1, time2;
cin >> time1 >> time2;
actions.push_back(Action(i, time1, true));
actions.push_back(Action(i, time2, false));
}
sort(actions.begin(), actions.end());
ll ans = 0;
for (int mask = 0; mask < (1 << n); mask++) {
if (ok(mask))
ans = (ans + 1) % mod;
}
cout << ans;
return 0;
}
